I have never seen a twist on "wire nut" ever used in a motor vehicle I have owned over the last 59 years, except in my RVs. (BMC, Chevy, Ford, AMC, Chrysler, Dodge, Mazda, Nissan or even my $699 Vespa car!
Wire nuts are used in stationary applications. Every car company in the world knows that. They might be ok for a "manufactured home" but should not be allowed by code in any RV. IMO as an engineer I would suggest filing a complaint with NHTSA for an unsafe electrical wiring fixture if you have somethnig actually burn out.
If there was a fire who would be at fault?
Retired Tire Design Engineer (40 years). I write a blog on RV tire applications www.RVTireSafety.NET and give seminars on RV tire application across the US. Serve on Technical Advisory Panel for FMCA.